1. Technical Field
The present disclosure relates generally to spinal implants and to spinal implant insertion instruments, and more particularly, to a spinal implant suitable for insertion into a receiving bed formed in the cervical region of the spine and to spinal implant insertion instruments adapted to facilitate the placement of an implant into a receiving bed formed in an intervertebral space.
2. Background of Related Art
Intervertebral implants for fusing together adjacent vertebrae of spinal column are well known in the art. Such implants are formed in a variety of different shapes and sizes and are configured for insertion into receiving beds formed in the various regions of the spine. Such implants are also formed of a variety of different biologically compatible materials including ceramics, polymers, human or animal bone, composites, etc. Intervertebral implants formed of natural bone may be formed of cancellous or cortical bone. Typically, due to its limited mechanical strength, implants constructed entirely from cancellous bone are used in the cervical region of the spine. In contrast, cortical bone has the mechanical strength suitable for use in any region of the spine. Because of its osteoinductive properties, it is more desirable to use a spinal implant constructed from cancellous bone where possible, than a spinal implant formed of cortical bone.
Instruments for positioning implants in a receiving bed formed between adjacent vertebrae are also well known. Such instruments include instruments for gauging the size of a receiving bed, instruments for grasping an implant and instruments for driving an implant into the receiving bed.
U.S. Pat. No. 4,566,466 discloses a surgical instrument for sizing a graft for insertion between distracted vertebral bodies. Each instrument includes a template head having a pair of spaced parallel flat surfaces separated by a predetermined distance. A handle is attached to the template head for grasping by a surgeon. A plurality of depth indicating lines are formed on the template head. In use, a surgeon inserts the template head of the instruments into a receiving bed formed between the distracted vertebral bodies to determine the size implant required for a spinal fusion procedure. The size of the required implant is determined when a template head fits snugly within the receiving bed.
U.S. Pat. No. 6,066,174 discloses an implant insertion device for gripping a surgical implant. The instrument includes a handle, a shaft having a proximal end attached to the handle, a pair of jaws attached to the shaft and a hollow sleeve slidably positioned over the jaws. The jaws are biased apart to a release position. The hollow sleeve is slidable over the jaws to urge the jaws from the release position to an approximated position in which the jaws are approximated to grip an implant. In order to slide the hollow sleeve over the jaws, a surgeon must grasp the handle with one hand and advance the hollow sleeve over the jaws with the other hand. Thereafter, the surgeon must apply constant pressure on the hollow sleeve to prevent the implant from falling from between the jaws.
Accordingly, a continuing need exists for a spinal implant having improved strength characteristics and osteoinductive properties. A continuing need also exists for implant insertion tools which can be operated by a surgeon using a single hand.
In accordance with the present disclosure, an intervertebral spacer formed of dense cancellous human or animal bone is provided. The implant may have a rectangular configuration or, in the alternative, may assume any configuration to meet a particular surgical requirement. In one preferred embodiment, the intervertebral spacer includes at least one bore which is dimensioned to receive a plug formed from cortical bone tissue. The cortical bone plug provided increased mechanical strength to the intervertebral spacer.
Instrumentation for gauging the size of an intervertebral receiving bed and for grasping and inserting an intervertebral spacer or implant into an intervertebral receiving bed are also provided. These instruments include a spacer trial or set of spacer trials for determining the appropriate size spacer required for a particular surgical procedure, a spacer introducer for grasping and positioning a spacer at least partially within a receiving bed formed in the intervertebral space, and a bone tamp for driving a spacer into the receiving bed. Any one or all of these instruments may be provided in a kit for inserting an implant into the intervertebral space. The kit may also include one or more intervertebral spacers or implants.